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Type of cabling supplying led vapourproof fittings

Baldyhugh

Hi all

ive a quick query I wouldn’t mind your opinion on. I have some ansell Tornado led vapourproof fittings to fit soon. They will be surface mounted using the supplied metal clips and the wiring will be pvc conduit and single stranded cable. I intend to enter the fittings through the end with a bit of flexible conduit and continue the stranded cable inside the fitting to the terminations which are about half way along the fitting. My query is that when the fitting is all assembled, the stranded cable will be resting on top of the metal ‘tray’ containing the led strips and driver which both actually give off quite a bit of heat after a while. Does ordinary stranded cable withstand a decent amount of heat? Previous fittings that I used had the terminations at one end so it wasn’t much of a problem but with this newer design, the incoming cable has to go half way up the fitting. I want to loop in/out inside the fitting instead of a plug in ceiling rose arrangement and don’t fancy having to put heat resistant sleeving  on each bit of stranded cable. Will the stranded cable survive lying on the metal tray long term?

Thanks in advance

  • 0

    It does sound a bit like the situation that 559.5.3 seeks to avoid. Probably less of an issue with LED than it was in the days of wound ballasts on fluorescents, but certainly worth considering all the same. PVC cables should be good to around 70 degrees but you'd probably have to check the light manufacturer's data for a value to compare with. It might make a difference if the control gear is off centre and you can approach from the other end as it were. The traditional solution of course was to design out the problem by mounting the fittings over a conduit box and use an entry point next to the terminals.

       - Andy.

  • 0

    Heat resistant glass fibre sleeving might be the solution inside the fittings. I have used it in old hot running tungsten bulkhead fittings, or where cables run past hot wound fluorescent ballasts.

    Z.

  • 0

    I assume the cable in the conduit is singles with PVC insulation.  (this sort of stuff - is rated for 70C )You can get singles insulated with other materials, (this stuff is in effect XPLE rated 90C)  (silicone rubbers go to 180c ) but not so easily. And then there is the question of being sure that it is adequately meeting other criteria as it is a non-standard wire choice. (rather like using SY someone will point out it is not on the approved list and ask you to jutify...) If you are only using a short run is it possible to use immersion heater flex style high temp cable rather than singles ? (I appreciate it may not suit the conduit choice)
    How hot do the LEDS get - can you ask the makers or fit one with a temperature sensitive label (these ones record the peak by darkening next to the highest temperature reached, a sort of high tide indicator - then you know the scale of your problem). It may not be as bad as you think.
    Mike

  • 0

    Thanks for your replies. It’s not actually the little driver that gets warm but the metal ‘tray’ that the two led strips are mounted on that gets warm after being on for a while that is giving me the concern. In the past I have suspended these fittings on chain so had to join my stranded to flex at each fitting and as such used heat resistant flex which did away with the problem. Unfortunately this particular type of fitting doesn’t allow for direct mounting on a conduit box or surface, they come with metal clips which are fixed to the surface first and then the body of the fitting clips onto this so that the whole fitting sits off the surface by about an inch. I’m trying the direct fitting rather than chain suspension on this job due to lower ceiling height and that it negates the need for a joint beside each fitting due to the fact that the fittings come with loop in / loop out toolless terminations for this very purpose. 

    Cheers

    Peter

  • 0

    If the LEDs, or their drivers, get hot enough to overheat 70C PVC cable, then they aren't going to last very long.

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